Method of using a hydraulic leveling circuit on an implement

ABSTRACT

The disclosure relates to a hydraulic circuit for a vehicle having a boom pivoted thereon by a boom ram and a bucket pivoted on the boom by a bucket ram. The hydraulic circuit includes a main pump that supplies fluid under pressure from a reservoir to the boom and bucket rams through control vales. An auxiliary circuit supplies fluid from the reservoir to the bucket ram to maintain the material handling unit at a predetermined attitude with respect to the reference plane and the auxiliary circuit includes a pump that is driven by the flow of fluid between the boom control valve and the boom ram.

United Stat es Patent 191 Seaberg [4 1 Dec. 24, 1974 METHOD OF USING AHYDRAULIC LEVELING CIRCUIT ON AN IMPLEMENT [62] Division oiSer. No.272,365, July 17, 1972. Pat. No.

3,311,587 a bucket pivoted on the boom by a bucket ram. The

hydraulic circuit includes a main pump that supplies [52 0.5. CI.214/152 fluid under Pressure from a reservoir to the boom and 51 Int.Cl. 865g 7/00 bucket rams through control vales- An auxiliary [58] Fieldof Search 214/140, 762, 763, 764, wit pp fluid from the reservoir to thebucket 1 214/152 ram to maintain the material handling unit at a prede-4 termined attitude with respect to the reference plane [56] I Referen sCit d and the auxiliary circuit includes a pump that is driven UNITEDSTATES PATENTS by the flow of fluid between the boom control valve3,032,215 5/1962 French et al 214/763 and the boom ram 3,563,137 2/1971Graber 214/763 3 Claims, 3 DrawingFigures 2 o I 36 52 40 t /8 a0 a I j'i T o W i J 2a 3 0 3,695,474 10/1972 Blakely 214/764 PrimaryExaminer-Robert J. Spar Assistant ExaminerRoss Weaver Attorney, Agent,or FirmDressler, Goldsmith,

Clement & Gordon, Ltd.

' [57] ABSTRACT The disclosure relates to a hydraulic circuit for avehicle having a boom pivoted thereon by a boom ram and 900mg: VALVPATENTEDUEC24|974- 3 f- FIG. 2

UNIT

VALVE 29/ (AUX; I06 //6 L70 (7 Z MOTOR MOTOR This is a division, ofApplication Ser. No. 272,365,

filed July 17, 1972 now U.S. Pat. No. 3,811,587.

FIELD OF THE INVENTION The present invention relates generally tomaterial handling equipment and more particularly to improved method andapparatus for controlling the position of a bucket supported on a boom.

In conventional. earth moving equipment, such as bucket loaders, theequipment generally includes one or more lift arms, generally referredto as a boom, pivotally carried on a vehicle with a bucket pivoted onthe free end of the lift arms. Generally, the lift arms are raised andlowered on the vehicle by a fluid ram having fluid supplied theretothrough a control valve while the bucket ispivoted on the end of thelift arms through an additional fluid ram having fluid supplied theretothrough a further control valve. The fluid is-generally supplied to therespective control valves from a reservoir through a pump. v

In normal operation, the bucket or material handling unit is positionedin a dig position and is forced into a pile of material by forwardmovement of the vehicle.

, The bucket is then pivoted or rolled back on the boom or lift armswith sufficient force to break out the mass of material within thebucket from the remainder of the pile.'Subsequently, the lift armsareelevated a sufficient distance to raise the bucket above the ground and2 mounted material handling unit. The auxiliary circuit supplies fluidfor maintaining the unit at a level condition and the amount of fluidsupplied is a function of thespeed at which the boom is raised andlowered with respect to the vehicle.

The method of the present invention contemplates supplying fluid underpressure from a reservoir through a main pump to first and secondcontrol valves that are selectively actuated to respectively control theflow of fluid to and from a boom ram and a material handling unit ram.Fluid for maintaining the unit at a level condition during the raisingand lowering of the boom is supplied through an auxiliary circuit thatincludes an auxiliary pump drivenby fluid flowingbetween the boom ramand its associated valve to deliver fluid from the reservoir to the unitram. In the specific method disclosed herein, the pump is a reversiblepump that is driven by an auxiliary motor inone of the conduits betweenthe boom ram and its associated valve so that fluid flow in eitherdirection in the conduit will drive the pump.

The method of the present invention is performed. with a hydrauliccircuit that supplies fluid to a boom ram that is capable of raising andlowering a boom pivoted on a vehicle and a unit ram that is capable ofpivoting a material handling unit on the boom. The hydraulic circuitincludes a reservoir with pump means for supplying fluid'under pressurefrom the reservoir.

' The hydraulic circuit also includes first hydraulic cirthe vehicle isdriven to some other location. Upon reaching the subsequentlocation, thebucket is pivoted to a dumping position where the contents aredischarged, after which the operation is repeated.

In an operation such as this, it is important that the bucket bemaintained at a level position while the lift arms are being raised andlowered to prevent the material or contents'from being spilled.

Many of the self-leveling devices take hydraulic fluid for levelingdirectly from the pump that also supplies fluidfor raising and loweringthe boomor lift arms.

In large units of this type, some difficulties have been encountered inhaving sufficient fluid available from the pump to allow the boom to beraised at its desired speed and at the same time provide the necessaryamount of fluid for performing the leveling function for the unit as theboom or lift arms are being raised and lowered.

Other self-leveling systems utilize slave cylinders between the liftarms and the support and fluid is directed from these cylinders to thebucket fluid rams during the raising and lowering of the lift arms toproduce the leveling function. However, the slave cylinders"self-leveling requires heavy mounting points for I the cylinders sincethey must absorb large forces developed by the hydraulic fluid as it isbeing transferred between the cylinders and bucket rams.

A furthersystem includes links that are interposed between the supportand the bucket and are usually carried by the lift arms to produce theleveling function. This type of system requires heavy links on top ofthe lift arms.

SUMMARY oF THE INVENTION The present invention incorporates an auxiliarycircuit into the normal hydraulic circuit for a vehicle cuit meansconnecting the pump and-reservoir to the boom ram and second hydrauliccircuit means connecting the pump means and reservoir to the unit ram.The hydraulic circuit further includes auxiliary hydraulic circuit meanscooperating with the first hydraulic circuit means and connected to thesecond hydraulic circuit means for supplying fluid under pressure fromthe reservoir to the unit ram and maintaining a predeter- -minedattitude of the material handling unit with respect to a reference planeas the boom is raised and lowered on the vehicle. Theauxiliaryhydrauliccircuit means incorporates an auxiliary pump that is driven by .fluidflow in the first hydraulic circuit means to supply fluid to the unitmotor for performing the leveling operation. v

More specifically, the first hydraulic circuit means includes a boomcontrol valve that is connected to the main pump and reservoir and tothe boom ram through first and second conduits. The second hydrauliccircuit means includes a unit control valve also connected to the mainpump and to the reservoir as well as being connected to the unit motorthrough first andsecond conduits. The auxiliary hydraulic circuit meansincludes an auxiliary motor in one of the conduits between the boomcoritrol valve and the boom ram with the auxiliary pump as a function ofthe flow of fluid in unit ram so that fluidunder pressure developed bythe auxiliary pump is available for performing the leveling function ofthe material handling unit.

In one embodiment of the invention, the auxiliary pump is connected tothe unit control valve which in-v corporates separate flow paths toallow fluid to be supquired for performing thelevelingfunction for thema terial handling unit.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF I DRAWINGS FIG. 1 is a schematicillustration of a vehicle having a boom pivoted thereon with a bucketpivoted on the boom with thehydraulic circuit of the inventionincorporated therein;

FIG. 2 is a'schematic illustration of thehydraulic circuit of thepresent invention; and,

FIG.- 3 is a slightly modified form of a hydraulic circuit.

DETAILED DESCRIPTION While this invention is susceptible of embodimentin many different forms, there is shown in the drawings and will hereinbe described in detail two specific embodiments, with-the understandingthat the present disclosure is to be considered asanexemplification ofthe principles of the invention and is not intended to limit theinvention to .the embodiments illustrated.

FIG. I of thedrawings generally shows the environment for the presentinvention and includes tractor or vehicle having upright supports 12 onopposite sides thereof (only one being shown). Each upright has .lift

arm 14 pivotally supported at the upper end on pivot pins 16. The liftarms define whatmay be termed a boom which has material handling unit orbucket 18 pivotally supported about pivot pins20. The lift arms or boomare adapted to be raised and lowered relative to the-vehicle throughboom ram 22 that consists of cylinder 24 pivoted on support 12 by pivotpin 26 withpiston rod 28 pivoted'on boom 14 by pivot pin 30. Again, twosuch boom rams are respectively attached between the two lift arms andthe supports on opposite sides of the vehicle.

Material handling unit or bucket 18 is pivoted on the outer end of boom14 through unit ram 32 cooperating with a parallelogram linkage thatconsists of links 34 and 36 pivotally interconnected at 38 andrespectively pivotally connected at 40 to the material handling unit andat 42 to lift arm 14. Fluid ram 32 consists of cylinder 50, trunionmounted on link 36 with piston rod 52 pivotally connected on lift arm 14by pivot pin 54. Two

unit rams 32 and links 34 and 36 are incorporated into the circuit andcooperate with the respectivelift arms 14.

ond conduit 68 connecting reservoir 68 to valve bank 66. The hyrdauliccircuit also includes first hydraulic circuit means 70 connecting valvebank 66 to boom The hydraulic circuit for supplying fluid to boomrams 22and'second hydraulic circuit means 72 connecting valve bank 66 to unitrams 32.

First hydraulic circuit means includes boom valve means 74, forming partof valve bank 66, and first and second conduits 76,78 connected-toopposite ends of cylinders 24. Second hydraulic circuit means 72includes unit valve means and first and second conduits 82,84 connectedto opposite ends of cylinders 50 forming part of unit rams 32. v

With the hydraulic circuit sofar described, actuation of boom valvemeans 74 in either direction from the neutral position will connectconduits 64 and 68 to conduits 76 and 78 to extend and retract pistonrods 28 thereby raising and lowering boom 14 with respect to vehicle 10;

Likewise, actuation of unit control valve means 80 in opposite directionfrom neutral position will connect conduits 64 and 68 to conduits 82 and84 thereby extending and retracting piston rods 52 with respect tocylinders 50 to pivot material handling unit 18 with respect to theboom.

As was indicated above, during the raising of the boom relative to thevehicle, when the material handling unit is filled with material, it isnecessary to constantly reposition the material handling unit whiletheboom is being raised to prevent the contents from being spilled. Itwill be appreciated that if the material handling unit is not constantlybeing repositioned, the attituide with respect to a reference plane willconstantly be changing as the boom is raised and lowered.

The present invention provides a simple system that eliminates the needfor having large and heavy pivotal connections, such asrequired intheslave cylinders system, and also eliminates the need forlarge links onthe lift arms so that the operators visibility is not effected by thepresent system. The system also has greater flexibility in the placementof components for the system.

. The present system to be described also maintains the advantage ofother hydraulic self-leveling systems and, at the same time, insuresthat there is always sufficient fluid available for performing theleveling as well as the lifting functions- According to the presentinvention, the hydraulic circuit incorporates an auxiliary hydrauliccircuit that becomes operative at any time the boom is raised andlowered to produce a separate sourceof fluid for the unit rams toperform the self-leveling function. With reference to FIG. 2, auxiliaryhydraulic circuit means is incorporated into the hydraulic circuit andcooperates with first hydraulic circuit means 70 for supplying fluidfrom reservoir 60 to unit ram 32 and the fluid supplied thereto iscapable of maintaining a predetermined attitude of the material handlingunit with respect to a fixed reference plane as the boom is raised andlowered on the vehicle.

Auxiliary hydraulic circuit means 100 includes reversible auxiliary pump102 having opposite sides or ports connected to reservoir 60 throughfirst and second conduits 104 and 106. First and second conduits 104 and106 each having unidirectional check valve 114 and each conduit, 110,112 has check valve means 116 to limit the flow of fluid in onedirection leading means 114. Auxiliary valve 114 is connected to first"and second conduits 82 and 84 through further conduits 120 and 122 andis also connected to reservoir 60 through conduit 124. 7 According tothe primary aspect of the present invention, auxiliary pump 102 isoperated as a function of the flow of fluid in first hydraulic circuitmeans 70. This is accomplished by auxiliary motor 130 in one of conduits76,78 with auxiliary motor 130 connected through shaft 132 to reversibleauxiliary pump 102.

With the auxiliary circuit incorporated into the main hydraulic circuitas shown and described, reversible auxiliary pump will only be operatedwhen fluid is flowing to and from boom rams 22. It will be appreciatedthat this arrangement substantially increases the service life'of theauxiliary pump since the pump will only be operating at times when fluidis necessary for maintaining the unit or bucket level.

Auxiliary 'valve 114 is actuated in response to a change in angularposition between material handling unit 18 and boom 14 while main unitcontrol valve 80 is in the neutral position. The actuating means forauxiliary valve 114 may take any, number of forms and a linkage system150 has been illustrated. By way of example, and not of limitation, themeans for actuating auxiliary valve 114 may be of the type illustratedin Horsch US Pat. No. 3,534,881; Horsch US. Pat. No. 3,578,191 andSeaberg et al. US. application Ser. No.

58,588 filed July 27, 1970, all assigned to the assignee of the presentinvention.

. The operation of the hydraulic circuit of the present invention 'willbe described in connection with the method aspect of the presentinvention. The pivoting of the boom on the vehicle and the materialhandling unit on the boom is accomplished by suppling fluid underpressure through pump 62 from reservoir 60 to first and second valves 74and 80, which are selectively actuated to supply fluid under pressure torams 22 and 32. The respective rams will pivot the boom on the vehicleand the material handling unit on the boom.'At any time fluid is beingsupplied to boom rams 22, auxiliary motor 130 will drive auxiliary pump102 in the appropriate direction to draw fluid from reservoir 60 througheither conduit 104 or 106 and supply this fluid under pressure throughthe other of the conduits to auxiliary valve 114. Auxiliary valve 114 isactuated when the angular position between boom.14 and mate- .rialhandling unit 18 is changed so that'the fluid supplied to auxiliaryvalve 114 will be directed to either conduit 82,84 while the other ofthese conduits is connected to reservoir 60 through conduit 124.

As can be seen from the description, the auxiliary hydraulic circuitproduces fluid under pressure for delivcry to unit rams 32 only whensuch fluid is necessary for producing the self-leveling function. Atother times,

auxiliary pump 102 is in a stationary condition thereby substantiallyincreasing the service'lifeof the unit. F urthermore, only a small pumpis necessary since the hydraulic fluid needed for the self-levelingfunction is rather small in comparison to the amount of fluid requiredfor supplying hydraulic rams 22 and 32.

A slightly modified form of the invention is shown in FIG. 3 and likereference numerals have been applied to the same parts. The onlydistinction betweenthe respective hydraulic circuits shown in FIGS. 2and 3 is that unit control valve means 800 and auxiliary valve means114a are incorporated into a single valve. This valve is of thecommercially available type wherein unit control valve 80a has a secondmidsection inlet 170 for receiving fluid from auxiliary pump 102 anddirecting this fluid through separate flow paths leading from inlet 170to the respective conduits 82 and 84. Since the combined main andauxiliary valve is commercially available from companies such asCommercial Shearing Co., Youngstown, Ohio, no detailed descriptionappears to be necessary.

Summarizing briefly, the present invention provides hicle by a boom ramand a material handling unit pivoted on the boom bya unit ram comprisingthe steps of supplying fluid under pressure through a pump from areservoir to first and second valves; selectively actuating. said valvesto supply fluid under pressure to said rams for pivoting the boom on thevehicle and pivoting the unit on the boom; and supplying fluid underpressure from said reservoir through an auxiliary circuit bypassing saidpump to the unit ram to provide fluid for maintaining a predeterminedattitude of said unit relative to a reference plane while the boom isbeing raised and lowered.

2. A method as defined in claim 1, in which said auxiliary circuitincludes .a pump and in which said pump is driven by'fluid flowingbetween said boom ram and the valve supplying fluid to said boom ram.

3. A method as defined-in claim 2, in which the pump in the auxiliarycircuit is reversible and there are first and second conduits betweenthe boom ram and the valve supplying fluid to the boom ram; and in whichthe pump in the auxiliary circuit is driven by fluid flowing in oppositedirections through one of the first and second conduits.

1. A method for controlling a boom pivoted on a vehicle by a boom ramand a material handling unit pivoted on the boom by a unit ramcomprising the steps of supplying fluid under pressure through a pumpfrom a reservoir to first and second valves; selectively actuating saidvalves to supply fluid under pressure to said rams for pivoting the boomon the vehicle and pivoting the unit on the boom; and supplying fluidunder pressure from said reservoir through an auxiliary circuitbypassing said pump to the unit ram to provide fluid for maintaining apredetermined attitude of said unit relative to a reference plane whilethe boom is being raised and lowered.
 2. A method as defined in claim 1,in which said auxiliary circuit includes a pump and in which said pumpis driven by fluid flowing between said boom ram and the valve supplyingfluid to said boom ram.
 3. A method as defined in claim 2, in which thepump in the auxiliary circuit is reversible and there are first andsecond conduits between the boom ram and the valve supplying fluid tothe boom ram; and in which the pump in the auxiliary circuit is drivenby fluid flowing in opposite directions through one of the first andsecond conduits.